In Science, changing ideas of inheritance.
As Darwin would have loved to have known, genes made of DNA are the basic unit of inheritance. But in recent years, researchers have shown that differences not related to DNA sequence can also be passed down, a phenomenon called epigenetic inheritance. Some studies have implicated chemical groups that bind to genes. A new study in mice, however, suggests other possibilities–some of which could dramatically alter our notions of inheritance.
Epigenetic inheritance has long been known in plants and yeast. In the mustard plant Arabidopsis, for example, epigenetic alterations in leaf and flower shape can be passed on to offspring. But the phenomenon was first demonstrated in mammals only in 1999, by molecular geneticist Emma Whitelaw and her coworkers. They created a strain of genetically identical mice, all of which had a coat color gene called agouti viable yellow (Avy). Despite having exactly the same DNA, the mice had wildly varying coat colors, ranging from yellow to mottled and nearly everything in between.